1. Field of the Invention
The present invention relates to an image processing method using an image processing device for detecting a specific detecting object from an image including a plurality of two-dimensionally arranged pixels, an image processing system to which the image processing method is applied, an image processing device used in the image processing system, and a computer program product for realizing the image processing device, and particularly relates to the image processing method, the image processing system, the image processing device, and the computer program product for improving a detection precision of the detecting object.
2. Description of Related Art
As a device to support driving a vehicle such as an automobile, there is proposed an image processing device for imaging a face of a driver by using an on-vehicle camera disposed at a position capable of imaging the face of the driver and performing image processing of detecting an outline of the face, positions of eyes and a nostril of the driver from the obtained image (for example, see Japanese Patent Application Laid-Open No. 2004-234367). By using such a device, it is possible to configure a system capable of detecting a condition of the driver and performing driving support such as a warning in accordance with the condition of the driver such as an inattentive driving and a drowsy driving. In addition, the situation that external light such as west sun shines in the face of the driver in the vehicle is intricately generated. Therefore, although an illuminance of the face of the driver during driving is not constant, a certain degree of adjustment is made by an auto gain function of the on-vehicle camera, so that a luminance of an image obtained by imaging the face of the driver becomes constant.
However, when the external light such as solar beam, reflective light, or the like is uniformly irradiated to the face of the driver, it is possible to respond to such a case by the auto gain function. However, when the external light is not uniformly irradiated, and the illuminance varies locally, the auto gain function for adjusting the luminance of an overall image can not respond to this case. For example, when one-sided variation occurs so that only left half of the face is exposed to direct solar beam, a dark portion of the face not exposed to direct solar beam can not be recognized as a face, thus generating a problem that an error detection occurs wherein only a bright portion of the face is detected as an outline of the face. In addition, when the error detection is performed to the face, there is a problem that the error recognition is also performed for a region that exists in a center of the face such as positions of eyes and nostrils.